Injection molding is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Injection molding machines include at least two mold mounting plates, with one mold mounting plate fixedly anchored upon a machine bed and with the other mold mounting plate movable relative thereto. The mold mounting plates carry respective half-molds, i.e. an upper mold and a bottom mold. Opening and closing of the cavity involves a displacement of the moving mold mounting plate or an upper mounting plate relative to the fixed mold mounting plate, i.e. a bottom mounting plate controlled by a mold closing unit. Material, such as thermoplastic or thermosetting plastic materials, is fed into a heated barrel, mixed, and forced into the mold cavity defined by the upper and bottom molds, where it cools and hardens to the configuration of the mold cavity in order to transform to a desired part or a product. Injection molding is widely used for manufacturing a variety of parts, from the smallest component to entire body panels of cars, and other parts.
The art of molding machines used in injection molding operations is replete with various designs with various mold closing units, some of them include a toothed locking bar attached to a movable mold mounting plate and penetrating the opposite facing stationary mold mounting plate through an opening. A control element is disposed at the opening for controlling the engagement of a pawl with the toothed locking bar wherein the pawl is movable into and out of engagement with the notches of the locking bar. The control element is activated by the positioning signals of a switch, which is actuated by the protective door when the protective door has reached open position. This type safety device requires relatively high expenditures with respect to mechanics and maintenance and in addition, the device itself also impedes accessibility to the space between the two mold mounting plates. Safety of the molding machines play a very important role during operation of the molding machine in order to minimize work related injuries on manufacturing floor.
One of such devices is taught by U.S. Pat. No. 7,179,074 to Zellerohr et al., which teaches two mold halves mounted to one of the two mold mounting plates. Attached to the movable mold mounting plate is a locking bar, which is provided with toothed notches and projects through an opening into the stationary mold mounting plate. A control member is secured to the stationary mold mounting plate, and operatively connected to a pawl, which can be brought into and out of engagement with the toothed notches of the locking bar for a locking, respectively an unlocking position. The locking bar and opening are disposed outside the mounting area of the mold halves and in the marginal area of the mold mounting plates. The device taught by the U.S. Pat. No. 7,179,074 to Zellerohr et al., is very complex and bulky and does not provide an alternative design that is compact and can serve several purposes such as clamping the upper mold to the housing and secure the upper mold in place in case of power outage and any external or internal impacts on the housing where the mold halves are positioned that may cause shutting or inadvertent drop of the upper mold against the bottom mold.
Another design is taught by U.S. Pat. No. 4,029,457 to Yamamoto, which discloses a molding machine of the type where a movable die plate carrying a movable mold is moved toward a stationary mold. The movable die plate is locked, by a locking member, to the tie bars. Then the mold-tightening cylinder is operated to strongly urge the movable mold against the stationary mold. The locking member is operated by an electric actuator before the movable mold engages the stationary mold, or while the movable die plate is still being moved toward the stationary mold. Similar to the device taught by the U.S. Pat. No. 7,179,074 to Zellerohr et al., the molding machine taught by the U.S. Pat. No. 4,029,457 to Yamamoto is very complex and bulky and does not provide an alternative design that is compact and can serve several purposes such as clamping the upper mold to the housing and secure the upper mold in place in case of power outage and any external or internal impacts on the housing where the mold halves are positioned that may cause shutting or inadvertent drop of the upper mold against the bottom mold.
Still another apparatus is taught by U.S. Pat. No. 5,211,970 to Sakurai et al., which discloses a hydraulic clamping apparatus for use with injection molding machines. The clamping apparatus includes a first hydraulic actuator having a first cylinder and a first hollow, cup-shaped piston with a closed head portion disposed for reciprocating movement within the first cylinder, a foot portion axially spaced from the head portion and defining an opening, a second hydraulic actuator having a second piston, a rod extending axially through the opening into the first piston and connected between the first and second pistons, a second cylinder mounted for reciprocating movement on the second piston and through the opening between a recessed position substantially within the first piston and an extended position substantially outside the first piston, and a clutch operable in the extended position of the second cylinder to produce engagement thereof with the first piston. The overall length of the apparatus is minimized by placement of the second actuator cylinder within the first piston.
U.S. Pat. No. 6,533,573 to Tamaki et al, discloses a mold clamping apparatus for an injection molding machine includes a stationary platen fixedly holding the stationary mold, a movable platen fixedly holding the movable mold and disposed opposite to the stationary platen, tie bars for guiding the movable platen for movement toward and away from the stationary platen, a movable platen driving mechanism for moving the movable platen along the tie bars to close and open the mold, a movable platen fixing mechanism for fixing the movable platen to the tie bars at a set position immediately before a position where the movable mold is joined to the stationary mold, and a clamping force applying mechanism including sealed hydraulic cylinder actuators capable of converting energy of a hydraulic fluid into an intensified mold clamping force and of applying the intensified mold clamping force to the stationary platen. In one embodiment, a rear plate located behind the movable platen carries a hydraulically driven ram support and clamping ram, and the ram support has a piston portion that is carried in a cylinder bore in the rear plate. The ram hydraulically clamps the mold closed after the movable platen is electrically driven to bring the mold halves together. The mold clamping apparatus taught by the U.S. Pat. No. 6,533,573 to Tamaki et al., for example, is very complex and bulky and does not provide an alternative design that is compact and can serve several purposes such as clamping the upper mold to the housing and secure the upper mold in place in case of power outage and any external or internal impacts on the housing where the mold halves are positioned that may cause shutting or inadvertent drop of the upper mold against the bottom mold.
Therefore, an opportunity exists for an improved molding apparatus for holding a mold assembly including upper and bottom mold portions that is simple in production and installation, and service and can serve several purposes such as clamping of the upper mold portion to the housing and secure the upper mold portion in place in case of power outage and any external or internal impacts on the housing thereby preventing shutting down or inadvertent drop of the upper mold portion against the bottom mold portion to eliminate any accident and injuries in a working environment during production process.
In addition, it would therefore be desirable and advantageous to provide an improved device for securing the upper mold portion of the injection molding machine by simple means, which obviates prior art shortcomings by preventing an inadvertent closing of the upper mold portion and to thereby realize improved security of operation as well as retaining good accessibility between the two mold mounting plates.